1. Field of the Invention
The present invention relates to a coating device for applying varnish over printed paper to prevent the paper from being made dirty and enhance an appearance of the paper.
2. Description of the Related Art
A diagrammatic construction of a conventional coating unit incorporated in a sheet rotary printer for applying varnish to printed paper to prevent the paper from being made dirty and enhance the appearance of the paper is shown in FIG. 6.
In FIG. 6, numeral 110 denotes a coating unit, 111 denotes a transfer drum, 112 denotes a pressure drum, 113 denotes a varnish application device, 113a denotes a varnish vessel, 113b denotes a main roller, 113c denotes an adjustment roller, 113d denotes an attachment roller, 113e denotes a rubber drum, and 114 denotes a drier.
In the coating unit 110, varnish in the varnish vessel 113a of the varnish application device 113 is supplied via the main roller 113b, the adjustment roller 113c and the attachment roller 113d to the rubber drum 113e. After the varnish is applied by the rubber drum 113e to a surface of paper which is transferred via the transfer drum 111 to the pressure drum 112, the paper is transferred via a paper discharge drum 103a to a paper discharge chain 103b. While the paper is conveyed, it is dried by the drier 114.
In some case, the varnish is applied not only to the printed surface but also to a rear face of the paper in order to enhance a waterproofness of the paper. However, in the conventional coating unit, the varnish can be applied only to one face of the paper. Therefore, when the varnish is applied to both faces of the paper, the paper is turned over after it is discharged. Then, the paper needs to be supplied again to the coating device for applying the varnish thereto. Efficiency is thus deteriorated.
To solve the problem, a construction is proposed in which there are provided two coating units between which a paper reversing mechanism is disposed, so that varnish can be applied to both faces of paper. In the construction however, since the number of units is increased, the printer is enlarged. It is difficult to ensure a space for installing the printer. Further, cost remarkably rises.
The problem arises in this manner not only in the coating unit incorporated in the sheet rotary printer for printing one face of paper but also in a coating unit for applying varnish to paper in general, e.g. in a coating unit incorporated in the sheet rotary printer for printing both faces of paper, or in a coating unit which is used independently without being incorporated in the printer.